OBJECTIVES: To evaluate the performance of 4-dimensional computed tomography (4D-CT) in assessing upper airway obstruction (UAO) in patients with Robin Sequence (RS) and compare the accuracy and reliability of 4D-CT and flexible fiberoptic laryngoscopy (FFL). STUDY DESIGN: Prospective survey of retrospective clinical data. SETTING: Single, tertiary care pediatric hospital. METHODS: At initial and 30-day timepoints, a multidisciplinary group of 11 clinicians who treat RS rated UAO severity in 36 sets of 4D-CT visualizations and FFL videos (dynamic modalities), and static CT images. Raters assessed UAO at the velopharynx and oropharynx (1-none to 5-complete) and noted confidence levels (LOC) of each rating. Intraclass correlation and Krippendorff’s Alpha were used to assess intra- and inter-rater reliability, respectively. Accuracy was assessed by comparing clinician ratings with Quantitative Percent Constriction (QPC) Ratings, calculated based on 4D-CT airway cross-sectional area. Results were compared using Wilcoxon rank-sum and signed-rank tests. RESULTS: 4D-CT and FFL demonstrated similar intra-rater agreement (moderate to substantial) and both demonstrated fair inter-rater agreement. Both modalities underestimated UAO severity, though 4D-CT ratings were significantly more accurate, as determined by QPC similarity, than FFL (−1.06 and −1.46 vs QPC Ratings, p=0.004). Overall LOC was similar for 4D-CT and FFL, but other specialists were significantly less confident in FFL ratings than were otolaryngologists (2.25 and 3.92, p